The present invention relates to an image position adjusting device in a printing machine. More particularly, the invention relates to the image position adjusting device for adjusting longitudinal image position relative to a printing sheet in an offset printing machine which is provided with a plate cylinder, a blanket cylinder, an impression cylinder and a sheet feed cylinder, and the adjusting device is capable of adjusting the longitudinal image position during operation of the offset printing machine.
U.S. Pat. No. 2,301,379 discloses an indexing apparatus for adjusting embossing or mortar line positions with respect to siding units such as those used in building walls by using an impression cylinder and an opponent roll. Even though the technical field is beyond the field of this invention, the technique described in this U.S. patent appears to be one of the prior art of the present invention.
According to the U.S. patent, as shown in FIG. 1, an impression cylinder 101 and a lower cylinder 102 are confronted with each other so as to nippingly interpose a siding 103. The cylinders 101 and 102 are connected to shafts 104 and 105, respectively. Further, a gear 113 is connected to the shaft 104 and another gear 114 is connected to the shaft 105. Each of the shafts 104 and 105 has one end rotatably supporting one end of each arms 106, 107, respectively. Another end of the arm 106 rotatably supports a first intermediate gear 108, and another end of the arm 107 rotatably supports a second intermediate gear 109. These intermediate gears 108 and 109 are meshedly engaged with each other. Further, the first intermediate gear 108 is in meshing engagement with the gear 113, and the second intermediate gear 109 is in meshing engagement with the gear 114 for drivingly connecting the cylinders 101 and 102.
The intermediate gears 108,109 are interposedly and rotatably supported by links 110 and 111. The link 110 is rotatably supported to a slider 112 which is slidable in a direction parallel to a line connecting central axes of the cylinders 101,102. By sliding the slider 112, relations of the gears 108,109 to the gears 113,114 is varied, whereby the angular rotational position of the impression cylinder 101 is adjusted so that any misalignment of the impressions relative to the length of the siding 103 is corrected.
If such structure is applied to an offset printing machine for adjusting the longitudinal imaging position in the printing sheet, the longitudinal position is controllable in a wide scale, that is, the output image can be largely displaced in the longitudinal direction by the sliding motion of the slider 112. However, to the contrary, fine control to the imaging position may be difficult to achieve. Further, disadvantageous rattling or looseness may occur at the gear trains having at least four gears in power transmission. Furthermore, it would be rather difficult to maintain the intermediate gears 108 and 109 at their predetermined controlled positions. Therefore, irregular rotations may occur between the impression cylinder 101 and the opponent cylinder 102. Moreover, the entire structure is rather complicated and requires a large number of mechanical components for assembly. Accordingly, the resultant device becomes costly.